> are his abilities required for the disciples to believe he is God?
His abilities aren't required, but Jesus did do them as signs to verify and confirm what he was saying. If Jesus were born as He was, didn't say a word, didn't do a thing, but then died on the cross and rose again, the same work would have been accomplished. The true issue is: Is Jesus the incarnated God? IF He's God, and came to Earth to die for our sins and rise again, that is all that is necessary.
But the teachings were meant to instruct and help us. We benefit from that kind of wisdom. And His miracles were meant as signs to confirm His deity in our eyes. (It's VERY common in the Bible for God to confirm His message with some kind of sign.) So that's what they were—but they're not required. Instead, they're helpful.
> doesn't his resurrection count as an amazing ability?
The NT says that God the Father raised Jesus from the dead (Acts 2.24, 32; 3.15, 26; 4.10; 5.30, etc.). Now, to be fair, since the Bible says Jesus and the Father are one and the same essence, Jesus says He will raise Himself from the dead (Jn. 2.19; 10.17-18). But you'll notice that in Jn. 2.19 He says He will raise Himself, and then in v. 22 it says He was raised (by God). Jesus's actions and God's actions are inseparable. Generally, putting it all together, we believe the Father raised Jesus from the dead (the habitual NT form of expression on this matter).
So, in direct answer to your question: No, His resurrection doesn't count as an amazing ability. It's the action that conquers the power of death, even if no one witnessed it. But Jesus DID allow people to witness it, so that our faith is based on evidence, not on blind faith.
> My reasons for believing that Jesus could be simply an alien or superhuman etc rather than the biblical God are things like:
Thank you for this.
> The problem of evil. Why does God allow things he considers evil?
This is a long and complex answer, but VERY briefly,
1. Evil and suffering can exist simultaneously with an "omni-" God as long as such evil and suffering have the possibility of good.
2. Evil and suffering can be allowed by an “omni-“ God where free will is necessary for humanity, which it is.
3. Evil and suffering can be allowed by an "omni-“ God because a dynamic world is superior to a static one.
4. God can use evil to beneficial ends (even though He doesn't perpetrate it).
There's much more. But am I to assume that since you have used this as a reason to discount God, you have read and studied this issue thoroughly? If so, then you know the arguments for the problem of evil are adequately addressed by Christianity.
> The elusiveness of God (why does he allow other religions?, why doesn't he appear today? etc)
Again, this is a long answer, but I'll write short. In the Bible we find that the more obvious God makes Himself, the greater the disbelief and the rebellion against Him. (Think Satan in who knows how long in the past, Adam & Eve, during the Exodus, and during the time of Jesus). It actually turns out as an aspect of human nature that the far wiser approach than obviousness is elusiveness—working inside the heart through the Spirit than in the empirical world of the eyes. We can talk about this more if you want.
> Why does God harm himself?
Because it's the only way. The only way to break out of prison is to be in prison. The only way to conquer death is to be dead first. The nature of life and death fixes certain realities. God just can't willy-nilly do this or that; His actions conform to what really is.
> Why does Jesus tell people to hate their families?
It's hyperbole to make a point. He's pushing their buttons, or they won't really get it. People are notoriously stuck in their mindsets. It takes quite a bit of disequilibrium to actually get a person to change their mind and their course in life.
> Why are people sent to hell for temporal crimes?
We don't know for sure that hell is eternal for everyone. What we know for sure is that God will be perfectly fair. If temporal punishment is what is fair for temporal crimes, then that is what will be. Our biggest takeaway from biblical talk about punishment after death is that God will not do anything that is in the least bit unfair. That's what you can hang you hat on.
> Why is slavery allowed, sometimes even condoned to some extent, in the Bible?
Slavery in the ancient world (Old Testament) was mostly debt slavery, much like our employment system. Chattel slavery was unknown in ancient Israel. First, the Israelites had been slaves themselves and we averse to slavery. Second, they were small family farmers and had little use or money for slavery. Third, the Bible speaks of the value of every human, so no one was treated as property. Fourth, therefore the "slavery" of the OT was more like indentured servitude, but "slave" was their word for it. It is never condoned. It was the teachings of the Bible that eventually undid slavery in the Roman Empire, and 18 centuries later in the colonial West.
Obviously all of these subjects demand a much longer discussion, but I can only put so much into one post. We can discuss any of them further if you want, but probably have to do so one at a time.
As a result, God, the way the Bible describes Him, is a far greater possibility of reality than an alien or a superhuman. Let's keep talking.